An electrical power delivery system is a complex system consisting of one or more generators with power flowing through cables to nodes, and then to loads. The functions required of the high-powered nodes are distribution, switching and power management. The functions of conversion and power conditioning are most appropriately handled at the branch level nodes. The node level functions are performed at high-power nodes in prior art legacy systems by circuit breakers and switch gear.
In the event of a fault, a prior art system may permit a high fault current, which has a potential for catastrophic collateral damage and which may also deprive other loads on the same or upwardly connected nodes of energy. When a fault occurs in the prior art system, a circuit breaker upstream from the fault opens. The prior art electromechanical circuit breaker may take up to 50 milliseconds to open for a high fault and 100 or more milliseconds for an intermediate fault. During these transient time periods, the systems upstream of the fault are perturbed. This perturbation is usually exhibited by a significant drop in voltage, particularly in close proximity to the fault, which may result in the voltage dropping to near zero for the period of time between the occurrence of the fault and the opening of the circuit breaker. This means that all loads being supplied by other circuits emanating from a node with a fault will experience a very low or zero voltage condition during the time of the fault. Sensitive loads may malfunction and some loads may become disconnected or may need to be reset or rebooted, causing them to be offline for a period of time significantly longer than the actual fault. This is obviously undesirable for sensitive and critical loads. Other loads may be transferred to alternate sources, which may cause further disturbances to the electrical system. In addition, there may be substantial arcing at the point of fault while the electromechanical circuit breaker is opening.
Such a scenario is shown in FIG. 1. In this example, there are 4 power panels (PP), each with six loads, fed from a load center node (LC). If a fault occurs at F1, with legacy equipment, the 18 loads in power panels #1, #2, and #3 will be deprived of power until the fault is cleared, which may take a minimum of 50 milliseconds and which could take as long as 400 milliseconds. The 6 loads in power panel #4 will be lost because the cable feeding them is faulted.
Therefore, it is desirable to find a replacement for the electromechanical circuit breakers that currently detect and switch off faulted circuits. In particular, it is desirable that the replacement for the electromechanical circuit breaker be able to detect a high fault within about 50 microseconds and be able to interrupt a high fault current in less than 400 microseconds. This represents an approximate thousand-fold increase in speed over prior art legacy systems. It is also desirable that the arcing that traditionally occurs when an electromechanical circuit breaker is opened be minimized or eliminated.